1. Field of the Invention
The invention relates to a high pressure gas tank, and more particularly, to a high pressure gas tank having a structure in which an outer periphery of a tank liner is covered by a fiber-reinforced resin layer.
2. Description of Related Art
An outer periphery of a tank liner of a high pressure gas tank is covered with fiber-reinforced resin. Japanese Patent Application Publication No. 2009-216133 (JP 2009-216133 A) describes technology in which gas venting holes are formed in fiber-reinforced resin in order to prevent residual gas that has permeated the tank liner and is trapped between the tank liner and the fiber-reinforced resin from being released outside all at once with release noise.
Moreover, Japanese Patent Application Publication No. 2009-191904 (JP 2009-191904 A) describes technology that inhibits the production of release noise of residual gas by melting a thermoset resin layer formed on an outermost peripheral portion of a fiber-reinforced resin layer to make it easier for the residual gas to pass through the thermoset resin layer.
A gas venting hole forming method described in Japanese Patent Application Publication No. 2009-216133 (JP 2009-216133 A) involves forming gas venting holes in a fiber-reinforced resin layer by producing minute cracks by injecting gas of equal to or greater than regular pressure between the tank liner and the fiber-reinforced resin layer. However, with this method, it is difficult to control the positions where the minute cracks are produced, so it is difficult to form gas venting holes evenly over the entire fiber-reinforced resin layer. If there is an area where no gas venting hole is formed in a portion of the fiber-reinforced resin layer, gas release noise will be produced in this area. Therefore, an attempt to inhibit gas release noise would require a separate process for inspecting the distribution of gas venting holes and selecting a tank in which the gas venting holes are distributed appropriately, which would increase both time and cost related to manufacturing.
Also, a manufacturing method described in JP 2009-191904 A involves using a solvent to melt a thermoset resin layer formed on an outermost peripheral portion of a fiber-reinforced resin layer. With this manufacturing method, it is difficult to form the thickness of the final thermoset resin layer evenly. Therefore, residual gas may end up being trapped locally in a portion where the thermoset resin layer is thickly formed, and as a result, a phenomenon in which residual gas ends up being released outside all at once with release noise is not able to be completely prevented.
Moreover, if a large amount of gas that will pass through the tank liner to the outside is generated locally, it will exceed the allowable limit of gas that is able to permeate the thermoset resin layer, so release noise at this portion is unable to be prevented.